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A computer system consists of several components which operate in different ways and at different speeds. The table below shows some of the major components:

Component Function
Central Processing Unit (CPU) Carrying out calculations, comparisons and logical operations
Random Access Memory (RAM) Storing data and programs temporarily while in use
Storage Devices Storing data and programs permanently: hard disks, CD/DVD drives etc.
Input / output Communication with the outside world: keyboard, printer, display etc.

One major function of an operating system (OS) is managing and coordinating the interaction between these components.

The other major function is to provide an interface between the user and the computer system by interpreting input from the user and producing output in a form understandable by the user.

The operating system is the most important item of software on a computer. It starts almost immediately after the computer is switched on and continues running until it is switched off again.

The operating system is the only program which talks directly to the hardware - all other programs, such as applications or games, communicate with the hardware via the operating system

Next: Types of OS